The contact print no matter how you decide you print this, is very small compared to the whole print. you can chose Rafts or Supports or none if you think your printer can handle it!
Cutting the tube
The Cap with the tube you get from Ebay is a tad too large for this print, a pair of scissors will take care of that, no need to be precise.
Designed in Inventor 2016 by Autodesk (highly recommended). Feel free to open my file on your computer and toy a bit with it, a learning experience as good as any.